Electromagnetic interaction pump



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ELECTROMAGNETIC INTERACTION PUMP Filed 001;. 5, 1953 5 Sheets-Sheet 1 inve or avoue-'y frase/e7- 77,-

Nov. 13, 1956 D. A. WATT ELECTROMAGNETIC INTERACTION PUMP 5 Sheets-Shes i 2 Filed Oct. 5, 1953 Attarney Nov. 13, 1956 v D. A. WATT 2,770,196

ELECTROMAGNETIC INTERACTION PUMP Filed oct. 5, 19m s sheets-sheet s INVENTOR WOLY W455i? WA,

ATTORNEY United States Patent ELECTRMAGNETIC INTERACTION PUlVIP Dudley Albert Watt, Oxford, England, assignor to United Kingdom Atomic Energy Authority, London, England Application October 5, 1953, Serial No. 384,090

7 Claims. (Cl. 103-1) The invention relates to single phase electromagnetic pumps for pumping liquid metals.

Known forms of single phase A. C. electromagnetic pumps include one due to Bainbridge (U. S. P. 1,660,407) and one due to Bruckel (D. R. P. 511,137).

It is an object of the present invention to provide an A. C. pump in which the exciting winding need not be in close proximity to the liquid metal circuit and which has an overall eliciency which makes the pump attractive compared with large scale D. C. pumps having regard to the fact that no auxiliary apparatus such as homopolar generators and rectifier banks is required to generate the high current used in the pump.

According to the invention a single phase electromagnetic pump for pumping` liquid metals comprises a closed primary iron circuit having a radially laminated part, a primary winding for said primary iron circuit, a duct of curved section around a length of said radially laminated part arranged to conduct liquid metal in a direction along that part, a partial secondary iron circuit comprising bridge members providing further radial laminations having one end in low reluctance contact with said radially laminated part and the outer end forming a pole piece around said duct and means for feeding liquid metal into and away from said duct.

A pump according to the invention is now described with reference to the accompanying drawings wherein:

Fig. 1 is a side elevation (diagrammatic in form) Fig, 2 is an elevation (diagrammatic in form) Fig. 3 is a plan view (diagrammatic in form) emphasizing the location of chokes.

Fig. 4 is a sectional view showing certain modifications of the embodiment shown in Figs. 1 to 3.

Fig. 5 is an elevation similar to Fig. 2 showing a modification of the presently disclosed invention.

Fig. 6 is an elevation similar to Fig. 2 showing still another form of the present invention.

Referring to Figs. 1 and 2 the pump comprises a closed primary iron circuit 10 having a radially laminated part 20 and parts 11, 12, 13 made up of flat laminations as shown. A primary winding 14 for the circuit 10 is provided on the part 13. An annular duct 22 is supported around the radially laminated part 20 and coupled with this duct is a series of inlet feed pipes 26 and outlet feed pipes 27 for liquid metal to be fed through the duct 22 by pumping forces created in the duct. A partial secondary circuit consisting of laminated bridge members 23 is also provided, the laminations being approximately radial, the end 16 being in low reluctance contact with the part 20 and the end forming a pole piece around the duct 22.

The pump can be visualised essentially as a transformer the secondary winding being the short annulus of liquid metal in the duct 22. The primary winding 14 is constructed with liquid cooled conductors. When the primary circuit is energised current lows in the secondary circuit of liquid metal. The secondary ampere turns magnetize the secondary iron circuit (which consists of ICC the bridge members 23 and the length of radially laminated part 20 under the bridge members) and produce a radial ilux at the pole formed by the ends 15, the flux traversing the liquid metal in duct 22. This radial ilux is substantially in phase with the secondary current which produces it; thus the current in the liquid metal reacts with the radial llux to produce a pumping pressure in the duct 22 in an axial direction. The end 15 is tapered to keep reactance ux and reactance voltage associated therewith to reasonable proportions.

The pump has some end current losses at entry and exit but these Iare reduced with the multiplicity of inlet and outlet pipes, the pipes forming, in effect, axial ballles at both ends of the annulus. The pipes are gathered in groups and brought together at headers 17. Between the duct 22 and headers 17 it is arranged that the pipes are kept out of electrical contact with one another. The pipes, together with the headers form closed loops around the transformer core at entry and exit and therefore some eddy currents in the pipe circuits exist. These currents are kept small by providing chokes 18, 19, in the form of iron laminations encircling the pipes (Fig. 3). The large chokes encircle several pipe groups on an axis of symmetry and the small chokes compensate for the unbalance between separate pipe groups. Ring type lamination stampings can be threaded along individual pipes to limit eddy currents in pipe loops within a group. Provided s'uicient laminated iron is used to counter the E. M. F.s in every pipe loop, however chosen, the currents which remain are magnetizing currents only.

A more detailed description of the pump is now made with reference to Fig. 4 of the drawings. Some additional modications are included in this ligure over the disclosure of Figs. 1 to 3. These modifications include reduction of liquid metal pipes 26, 27 to four, the reduction of secondary bridges 23 from six to four and the showing of a tapered pole piece.

Referring now to Fig. 4 the part 20 has radial laminations 21 and supports the heat insulated annular duct 22 and four laminated bridges 23. The annular duct is constructed of high resistance stainless steel and has welded to it four inlet ports 24 and four outlet ports 25. These ports form into tubes 26 and 27 respectively. Heat insulation is provided by asbestos rings 28, 29.

The laminated bridges 23 having tapered faces 30 thereby introduce the modification referred to of a tapered alr gap.

The radial laminations for part 20 may be constructed by placing two machined wedge sections of equal angle back to back to form a parallel sided section, uniting corresponding yedges of the section together and rolling along the length of the parallel sided section whilst hot (700 C.). Sprayed alumina is provided between the Wedge sections to prevent welding together of the sections when rolled.

In a modification of the invention as shown in Fig. 5 the duct 22 is iitted with longitudinal high conductivity bars 31, such as copper bars. Where contact potentials between these bars and the liquid metal is low a larger secondary current can be achieved than with an annulus completely lled with poor conductivity liquid metal. The hydraulic flow is also modified in this manner. The high conductivity bars are arranged to coincide with gaps around the pole formed by the laminated bridge members.

Alternatively the subdivided duct of the above modiication may be regarded as a thick copper sleeve having a plurality of longitudinal gaps for the passage of liquid metal and may be constructed, as shown in Fig. 6,

the reverse direction at low power by providing an auxiliary primary winding 34 under the bridge members 23 and switch means 35 to energize either of the primary windings separately. Such a Winding would require to be capable of withstanding the high temperature conditions prevailing adjacent the annular duct 22 and would be used instead of the main primary winding 14 to obtain low power reverse ow for special purposes, such as for transferring the liquid metal from one part of the circuit to another during maintenance.

I claim:

1. A single phase electromagnetic pump for pumping liquid metals comprising a closed primary iron circuit having a radially laminated part, at least one primary winding for said primary iron circuit, a duct of curved section around a length of said radially laminated part arranged to conduct liquid metal in a direction along that part, a partial secondary iron circuit comprising bridge members providing further radial laminations having one end in low reluctance contact with said radially laminated part and the other end forming a pole piece around said duct and means for feeding liquid metal into and away from said duct.

2. A pump as claimed in claim 1 wherein the end of said partial secondary iron circuit forming a pole piece is tapered in a sense to reduce fringing ux at the pump inlet.

3. A pump as claimed in claim 1 wherein the means for feeding liquid metal into and away from said duct comprises a multiplicity of pipes and laminated chokes, each choke embracing at least one of said pipes.

4. A pump as claimed in claim 1 wherein said duct is supported in heat insulating means to minimise heat conduction from the liquid metal to the magnetic circuits.

5. A pump las claimed in claim 1 wherein said duct is tted with longitudinal high conductivity bars.

6. A pump as claimed in claim 1 wherein said duct is subdivided into a plurality of separate pipes and a 1ongitudinal bar of high conductivity metal is arranged between adjacent pipes to form a conducting sleeve.

7. A pump las claimed in claim 1 having an auxiliary primary winding under said bridge members and switch means for energising either of said primary windings separately.

References Cited in the file of this patent UNITED STATES PATENTS 2,386,369 Thompson Oct. 9, 1945 2,539,800 Tama Jan. 30, 1951 2,612,109 Wakefield Sept, 30, 1952 2,655,107 Godbold Oct. 13, 1953 2,669,183 Godbold Feb. 16, 1954 

